Timestamp Converter - Unix Timestamp Online Converter

1. Two-way conversion and unit auto-detect

The key concept: **a timestamp has no time zone** — it is an absolute moment. "Eight hours off" lives in the formatting layer; "1000× off" lives in the unit layer (ms read as seconds or the reverse). When values disagree, unify units first, then UTC vs local display.

1. Timestamp → date: paste a numeric stamp; auto mode classifies s / ms / µs / ns by magnitude and shows local, UTC, ISO, and relative time.
2. Date → timestamp: pick a datetime to get common-precision stamps.
3. Batch: one stamp per line; bad lines error individually while others still convert — handy for a column scraped from logs.

2. Rules every developer should know

• Store UTC timestamps always; convert to local only at the display layer — storing local time in a database is the mother of all bugs.
• Rough digit counts: ~10 s, ~13 ms, ~16 µs, ~19 ns; for boundary values trust auto instead of mental arithmetic alone.
• Mind the 2038 problem: 32-bit second stamps overflow — use 64-bit in new systems.
• Log comparison: servers on UTC, containers possibly without TZ set, your laptop at UTC+8 — unify the base first.

3. Three hidden traps in JavaScript date handling

First, Date.getMonth() returns 0-11 — January is 0, and that off-by-one has caused countless incidents. Second, new Date('2026-01-01') and new Date('2026/01/01') parse differently (ISO date strings anchor to UTC midnight, slash format to local time), so identical code drifts across browsers and locales. Third, Date.parse tolerance for non-standard formats varies by engine — Safari historically returns NaN for '2026-01-01 00:00:00' (space-separated). Engineering conclusion: parse inputs exclusively via ISO 8601 or explicit year/month/day components, and delegate formatting to Intl.DateTimeFormat rather than hand-built strings.

4. Timestamp practices inside databases

• MySQL TIMESTAMP columns convert through the session time zone (readings shift when it changes), while DATETIME stores a literal — teams must agree on which zone the literal means.
• PostgreSQL timestamptz stores an absolute UTC instant and renders per session zone — closest to the timestamp's true semantics; prefer it for new projects.
• Encode the unit in the column name or docs (created_at_ms); a bare created_at is a ticking bomb during debugging.

5. Mental math: mapping timestamps to decades

A few anchors worth memorizing: 10-digit 1600000000 = Sep 2020, 1700000000 = Nov 2023, 1800000000 = Jan 2027. On seeing an unfamiliar stamp, check length and leading digits first: 13 digits starting 17-18 means 2020s milliseconds; 10 digits starting 1.7-1.8 means 2020s seconds. Coarse anchoring saves repeated round-trips to a converter during log triage.

6. Where µs / ns come from: Go, Java, and digit explosion

Beyond familiar seconds and milliseconds, modern runtimes often emit microseconds or nanoseconds: Go’s time.Now().UnixNano(), some Java Instant serializations, high-resolution trace spans. Rough bands: seconds < 1e10, milliseconds < 1e13, microseconds < 1e16, then nanoseconds — this tool’s auto mode follows that split (a past bug treated 19-digit values as seconds; it now classifies them as ns). If you already know the unit, lock it in the UI so extreme boundary values are not classified into the neighboring bucket.